Max fstop of Sigma 50-500 @ 300mm & 400mm?

I already know that the max fstop of the Sigma 50-500 from 50-200mm

is f4, and it's f6.3 @ 500mm, but what's the max fstop at 300mm and

400mm respectively?

 

ps. I've already google'd the net & pnet, and did not find the

answer, and Sigma's site did not have the answer either.

Unfortunately its f6.3 at those focal lengths...one of the reasons I sold mine and bought the 300mm f4 AFS. Its a great lens if you don't need the speed. Super optics, great construction, handles beautifully, and very fast focusing.